Array improperly loading

I have an array in my game that is set as active prior to pressing play (see fig.1) but as soon as I press play, it doesn't load properly (see fig.2). Each element is a prefab, and the prefabs all have the same settings, so I can't figure out why only some are loading. The Object Spawner script is what I use for it, and array was working just fine when I only had three elements, but when I added the fourth it stopped working properly. Can anyone see what I'm doing wrong?

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class ObjectSpawner : MonoBehaviour
6. {
7.     public GameObject player;
8.     public GameObject[] trianglePrefabs;
9.     private Vector3 spawnObstaclePosition;
10.  
11.    
12.     // Update is called once per frame
13.     void Update()
14.     {
15.         float distanceToHorizon = Vector3.Distance(player.gameObject.transform.position, spawnObstaclePosition);
16.         if (distanceToHorizon < 120)
17.         {
18.             SpawnTriangles();
19.         }
20.     }
21.     void SpawnTriangles()
22.     {
23.         spawnObstaclePosition = new Vector3(0, 0, spawnObstaclePosition.z + 30);
24.         Instantiate(trianglePrefabs[(Random.Range(0, trianglePrefabs.Length))], spawnObstaclePosition, Quaternion.identity);
25.     }
26. }
27.  

 

The blue box disappears from elements 1 and 4 on play, so from the look of it, element 1 and 3 are not actually prefabs. They seem to be referencing an instance of a prefab in the scene, rather than the prefab itself that is in the project view.

 

You are a hero, this is exactly what the problem was. Many thanks!